This application claims the benefit, under 35 U.S.C. xc2xa7 119, of Korean Patent Application No. 2000-8969, filed on Feb. 24, 2000, the entirety of which is hereby incorporated by reference for all purposes as if fully set forth herein.
1. Field of the invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a structure of a liquid crystal display module having metallic frames for fixing a back light unit and a liquid crystal display panel.
2. Description of Related Art
Liquid crystal displays (LCDs) are gaining in popularity for use in systems such as television receivers, computer monitors, avionics displays, aerospace displays, and other military-related displays where the elimination of cathode ray tube (CRT) technology is desirable for several reasons. In particular, CRTs are characterized by large depth dimensions, undesirably high weight, and fragility. Additionally, CRTs require a relatively high voltage power supply in order to sufficiently accelerate electron beams for displaying images.
The aforementioned shortcomings of CRTs are overcome by flat panel liquid crystal displays in which matrix arrays of liquid crystal picture elements or pixels are arranged in a plurality of rows and columns. In general, LCD devices have various advantages in comparison with CRT display devices in that they are thin in thickness and low in power consumption, etc. Therefore, such LCD devices might be expected to be substituted for CRT display devices and have been a matter of great interest in some industry fields.
In contrast to the CRT, the liquid crystal display device requires a light source, because the liquid crystal is not a fluorescent material. A cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL) or the like is used as the light source of the liquid crystal display device. The lamp is included in a back light unit of the liquid crystal display device. Back light units are classified into direct back light type (or direct type) units and edge light type (or edge type) units, according to a position of the lamp.
In the case where the direct type back light unit is used for a liquid crystal display device, incident rays irradiating from a lamp are directly incident to a liquid crystal display panel after a diffusion sheet uniformly diffuses the incident rays. In the case where the edge type back light unit is used, rays from a lamp are incident to a liquid crystal display panel via a light guide. A detailed explanation of the edge type will be provided subsequently.
The edge type back light unit generally includes a lamp, a light guide on a side surface of the lamp, a diffusion sheet on the top surface of the light guide, and a reflection sheet on the bottom surface of the light guide. The light guide uniformly scatters rays irradiating from the ramp such that rays are uniformly incident on the diffusion sheet. The reflection sheet reflects rays directed opposite to the diffusion sheet such that most of the rays from the lamp are incident on the diffusion sheet. The diffusion sheet diffuses the rays to provide a uniform luminance throughout a light exit surface of the diffusion sheet. Additionally, a set of two prism sheets is beneficially disposed on the light exit surface of the diffusion sheet. The prism sheet set selectively changes the light rays as they pass through the sheets such that the luminance is enhanced at a particular viewing angle range. The rays from the prism sheet set are incident to the liquid crystal display panel of the liquid crystal display device such that images are displayed.
A mold frame of the liquid crystal display device supports the back light unit including the above-mentioned sheets and lamp such that the liquid crystal display panel and back light unit are fixed with each other in a fixing structure. However, as the liquid crystal display device becomes thinner and thinner, the fixing or supporting structure of the above-mentioned back light unit including the light guide et al. becomes more difficult to design. That is to say, a space for fixing the back light unit is so limited that a merely normal impact may break the fixing structure of the back light unit.
With reference to FIGS. 1 and 2, a conventional fixing structure of the back light unit will now be provided. FIG. 1 is a plan view illustrating a lower frame made from a plastic with a molding, and FIG. 2 is a cross-sectional view illustrating how the back light unit is assembled with the conventional lower frame in a typical liquid crystal display module.
As shown in FIG. 2, a typical liquid crystal display module 10 includes an upper frame 20 and a lower frame 30, which oppose each other. A liquid crystal display panel 60 and a back light unit 40 are disposed between the upper and lower frames 20 and 30. The liquid crystal display panel 60 includes first and second substrates (not shown) and a liquid crystal layer (not shown) sandwiched therebetween. The back light unit 40 is the edge type and includes a lamp 44, a light guide 42, a reflection sheet 48, a diffusion sheet 45, and a prism sheet 46. A panel guide 50 is further interposed between the upper and lower frames 20 and 30 and supports the liquid crystal panel 60.
As shown in FIG. 1, a conventional lower frame 30, having the lamp (reference 44 in FIG. 2) at a first side (a long side), includes a rib 32 at each second side (short side) perpendicular to the first side where the lamp is disposed. The ribs 32 fix the light guide 42. In addition, the lower frame 30 includes protrusions 34 at one of the second sides to fix the various sheets (reference 46 and the like in FIG. 2).
In assembling the back light unit 40 of FIG. 2 with the lower frame 30 of FIG. 1, at first, the lamp 44 is disposed on a long side of the lower frame 30. Then, the reflection sheet 48 is mounted on the lower frame 30, and the light guide 42 is mounted on the reflection sheet 48. Thereafter, the diffusion sheet 45 and prism sheet 46 are sequentially mounted on the light guide 42. At this point, a double-coated tape (not shown) is used between the diffusion and prism sheet 45 and 46 to fix their relative position.
Returning to FIG. 1, the ribs 32 and protrusions 34 serve to fix the light guide 42, diffusion and prism sheets 45 and 46 (see FIG. 2) such that a defect due to a movement thereof is prevented. Specifically, the ribs 32 prevent the movement of the light guide 42, and the protrusions 34 prevent movement of the diffusion and prism sheets 45 and 46. Each protrusion 34 has a cylindrical shape and protrudes upward from the rib 32 disposed at one of the second sides of the lower frame 30.
Meanwhile, the number of lamps used in the conventional art is increased in order to improve the brightness of the large scale LCD device, and thus the power consumption increases. However, some problems occur in the LCD device because of the heat from the lamp as well as a printed circuit board (PCB), which is conventionally interposed between the upper and lower frames and electrically connected with the liquid crystal display panel. That is to say, the lower frame is conventionally made with plastic molding, and since plastic has poor thermal radiation and conductivity properties, heat from the lamp or PCB cannot be conducted or radiated away. This causes heating of the liquid crystal display panel, a deterioration of luminance, and a wrinkle in the sheets.
To solve the problems caused by the heat, the lower frame 30 is beneficially made of a metallic material, usually aluminum (Al) that has good thermal conductivity and good thermal radiation. However, at this point, since the rib and protrusions are difficult to form on a metallic lower frame, additional elements are needed to fix the light guide and sheets.
Accordingly, the present invention is directed to an LCD module that substantially obviates one or more of the problems due to limitations and disadvantages of the related art, while retaining its advantages.
An object of the present invention is to provide an LCD module having an effective fixing structure to fix a light guide and various sheets of a back light unit.
Another object of the invention is to provide an LCD module that improves heat transfer.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
In order to achieve the above object, the present invention provides a liquid crystal display module which includes: a back light unit device having a) a lamp, b) a reflection sheet reflecting light from the lamp, c) a light guide positioned over the reflection sheet, the light guide having grooves at opposing sides, and d) a plurality of sheets located over the light guide, each sheet having a through hole corresponding to the grooves of the light guide; a liquid crystal panel located over the back light unit; a first frame located over the liquid crystal panel; a second frame having a) a main portion under the back light unit, b) first and second wall portions perpendicular to the main portion and disposed on sides of the main portion, and c) supporting portions extending outwardly from the first and second wall portions and parallel to the main portion, the supporting portions having first fastening means; and a fixing unit having a) pressing portions parallel to the supporting portions of the second frame, the pressing portions pressing down the grooves of the light guide, b) protrusions protruded upward from the pressing portions, the protrusions being inserted into the through holes of the plurality of sheets, and c) a connecting portion parallel to the supporting portion of the second frame, the connecting portion having a second fastening means for fastening with the first fastening means of the second frame.
The first fastening means of the second frame is beneficially a screw hole, the second fastening means of the fixing unit is beneficially a through hole, and beneficially a fastener such as a bolt or screw is driven into the screw hole and the through hole such that the second frame and fixing unit are assembled. The protrusions and pressing portions of the fixing unit are integrally formed.
The fixing unit is beneficially plastic, while the second frame is beneficially made of metal.
A lower surface of the groove of the light guide is on the same plane as an upper surface of the supporting portion of the second frame, and a lower surface of the pressing portion of the fixing unit is on the same plane as a lower surface of the connecting portion of the fixing unit.
The groove of the light guide further includes an opening or notch opened in an outward direction, and the fixing unit further includes a perpendicular portion such that the opening in the groove receives the perpendicular portion.
The liquid crystal display module further includes a radiation plate, the radiation plate being disposed over the lamp of the back light unit and contacting the supporting portion of the second frame. The radiation plate beneficially is made of aluminum (Al).
The back light unit beneficially includes a plurality of lamps.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.